1. Field of the Invention
The present invention relates to an electronic zooming device for vertically or horizontally resizing (change of image size), for example, two-dimensional image data obtained by image-processing a video signal outputted from an image sensor developed for a digital camera depending on how the image data is used.
2. Description of the Related Art
In recent years, there has been a remarkable progress in the transition from the analog technology to the digital technology in the camera industry. A digital still camera, in particular, for which neither a film nor a developing process is necessary, is selling well in the market. Further, mobile telephones in the mainstream are now provided with a built-in camera, and not only an optical zooming device but also an electronic zooming device is installed therein to process a digital signal. In a digital still camera, resizing of an obtained image or a reproduce image is functionally useful as a means for adjusting an image size in accordance with a display device, and as a band-limited image transmitter.
So far were proposed, as the digital still camera, an electronic zooming device for scale-down resizing which allows a data size of an obtained image file to be reduced and makes it easier to handle the image size, and an electronic zooming device for scale-up resizing which enables the details of the obtained image to be checked on a liquid crystal monitor (for example, see Japanese Patent Laid-Open Publication No. 2000-134524).
FIG. 5 shows a conventional electronic zooming device. Referring to reference numerals shown in the drawing, 501 denotes a solid-state image sensing device for photoelectrically converting an optical image of a photographic subject and outputting charge information, 502 denotes a CDS/AGC circuit for retrieving a charge signal obtained from the solid-state image sensing device 501 as an analog signal, 503 denotes an A/D converter for converting the analog signal obtained in the CDS/AGC circuit 502 into digital video data, 504 denotes a pre-processor for executing the black-level correction, gamma correction, gain correction, and the like, to the A/D-converted image signal data, 505 denotes a YC input unit for inputting a digital YC signal from outside, 506 denotes a medium input unit for receiving the image data inputted from an external medium input unit, 507 denotes a SDRAM in which the respective image data is stored, 508 denotes an image processor for converting the pre-processed data into YC data, 509 denotes a vertical zooming unit for vertically resizing the inputted image data by a tap number m, 510 denotes a horizontal zooming unit for horizontally resizing the vertically resized image data obtained in the vertical zooming unit 509 by a tap number n, and 511 denotes a memory controller for controlling the input and output of the data between (the pre-processor 504, SDRAM 507, YC input unit 505, medium input unit 506 and image processor 508) and (vertical zooming unit 509 and horizontal zooming unit 510). The tap number mentioned above denotes the number of digital filter coefficients.
In the electronic zooming device, the memory controller 511 inputs the image data to be resized to the vertical zooming unit 509. The vertical zooming unit 509 vertically resizes the image data using a fixed coefficient of the tap number m in accordance with a vertical resizing magnification, and inputs one horizontal data which was vertically resized to the horizontal zooming unit 510. The horizontal zooming unit 510 horizontally resizes the inputted data using a fixed coefficient of the tap number n in accordance with a horizontal resizing magnification. As a result, the data which was horizontally and vertically resized can be obtained.
However, the foregoing conventional electronic zooming device was provided with only such a single function of resizing image data by means of a fixed tap coefficient predetermined in accordance with the magnification.